Silicon dioxide solar cell

ABSTRACT

In order to increase the generation efficiency of a silicon dioxide solar cell, two conductive substrates are arranged so that the conductive surfaces thereof face each other, at least one of the substrates is disposed upon the substrate facing the light entry-side substrate, and an electrolyte is filled between the silicon dioxide particles compact and the light entry-side substrate. Silicon dioxide solar cells having this configuration exhibit a significantly increased short circuit current and open circuit voltage in comparison to solar cells in which the silicon dioxide and the electrolyte are mixed. This configuration can further be improved by disposing a titanium dioxide solar cell or a dye-sensitized titanium dioxide solar cell upon the light entry-side substrate to further increase the short circuit current and the open circuit voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.14/004,283, filed Sep. 10, 2013, which is a U.S. National Stage entry ofInternational Application No. PCT/JP2012/056291, filed Mar. 12, 2012,which claims priority to Japanese Patent Application No. 2011-054609,filed Mar. 11, 2011, Japanese Patent Application No. 2011-073152, filedMar. 29, 2011, Japanese Patent Application No. 2011-091389, filed Apr.15, 2011 and 2012-044753, filed Feb. 29, 2012, the entirety of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a solar cell, more particularly to asilicon dioxide solar cell using silicon dioxide.

BACKGROUND ART

A dry-type solar cell using a semiconductor, such as silicon, is on thestage of being practically used. A semiconductor solar cell has highgeneration efficiency, but is expensive due to the use of a highlypurified material.

As a relatively inexpensive solar cell, there is a wet-type solar cellusing titanium dioxide (TiO₂) and an electrolyte.

A titanium dioxide solar cell arrangement is described with reference toFIG. 1.

FIG. 1(a) shows a titanium dioxide solar cell having a basicarrangement, and FIG. 1(b) shows an improved titanium dioxide solar cellcalled a dye sensitized type. In the titanium dioxide solar cell havingthe basic arrangement shown in FIG. 1(a), numeral 1 represents a glasssubstrate forming on one surface thereof a transparent conductive layer2 made of FTO or the like, and which serves as a photoelectrode. Numeral3 represents a porous titanium dioxide sintered material. Numeral 4represents an electrolytic solution, and an iodine electrolyte havingiodine dissolved in an aqueous potassium iodide solution is generallyused. Numeral 5 represents a platinum counter electrode which is formedon a glass having formed thereon a conductive layer 6 made of FTO or thelike. Numeral 8 represents a sealing material, and numeral 9 representsan external load, such as a resistor.

The incident light which has passed through the transparent conductivelayer 2 on the glass substrate 1 is absorbed by the porous titaniumdioxide sintered material 3. The porous titanium dioxide sinteredmaterial 3 which has absorbed the light is electronically changed fromthe ground state to an excited state, and the excited electrons arecaused to go out of the transparent conductive layer 2 due to diffusion,and introduced through the load 9 from the transparent conductive layer6 to the platinum counter electrode 5.

However, the light which the titanium dioxide can utilize in electricgeneration is only ultraviolet light having the wavelength of 380 nm orless, and the ultraviolet light in this range of wavelength is only 4%of the sunlight, and thus the sunlight utilization efficiency is 4% atmost, practically 1%, and therefore, this solar cell using titaniumdioxide exhibits extremely poor utilization efficiency of the sunlight.

For removing the drawback of titanium dioxide that the usable wavelengthrange of light is narrow, there has been known a dye sensitized solarcell (DSSC) which has sintered porous titanium dioxide having aruthenium complex dye adsorbed thereon, and which thereby can use lightin the visible light region that is longer in wavelength than theultraviolet light.

The basic arrangement of the dye sensitized solar cell is described withreference to FIG. 1(b).

In this figure, numeral 1 represents a glass substrate forming on onesurface thereof a transparent conductive layer 2 made of FTO or thelike. Numeral 3 represents a porous titanium dioxide sintered materialhaving a ruthenium complex dye adsorbed on the porous surface thereof.Numeral 4 represents an electrolytic solution, and an iodine electrolytehaving iodine dissolved in an aqueous potassium iodide solution isgenerally used. Numeral 5 represents a platinum counter electrode whichis formed on a glass substrate 7 having formed thereon a conductivelayer 6 made of FTO or the like. Numeral 8 represents a sealingmaterial, and numeral 9 represents an external load, such as a resistor.

The incident light which has passed through the FTO transparentconductive layer 2 on the glass substrate 1 is absorbed by the rutheniumcomplex dye adsorbed on the porous surface of the porous titaniumdioxide sintered material 3. The ruthenium complex dye which hasabsorbed the light is electronically changed from the ground state to anexcited state, and electrons in the excited state in the rutheniumcomplex dye are injected into the porous titanium dioxide sinteredmaterial 3, so that the ruthenium complex dye changes to an oxidationstate. In this instance, for effectively injecting the excited electronsin the ruthenium complex dye into the porous titanium dioxide sinteredmaterial 3, the excitation energy level of the ruthenium complex dyemust be lower than the conduction band energy level of the poroustitanium dioxide sintered material 3 which is a semiconductor. Theelectrons injected into the porous titanium dioxide sintered material 3are caused to go out of the transparent conductive layer 2 due todiffusion, and introduced through the load 9 to the platinum counterelectrode 5. On the other hand, the oxidized ruthenium complex dyereceives electrons from iodine contained in the iodine electrolyte 4 andis changed back to the ruthenium complex dye in the ground state.

A dye sensitized solar cell having the above-mentioned arrangementtheoretically has sunlight utilization efficiency of 30%, but,practically 10% at most.

Titanium dioxide has a photocatalytic function, and, as a materialsimilarly having the photocatalytic function, fused quartz treated withhalogen acid is described in JP-A-2004-290748 and JP-A-2004-290747.

As a material similarly having a photocatalytic action, synthetic quartztreated with hydrofluoric acid is described in International PatentApplication Publication No. WO2005/089941.

The synthetic quartz photocatalyst functions as a photocatalyst in awavelength range of 200 to 800 nm which is further wider than the rangefor the photocatalyst using fused quartz as a raw material described inJP-A-2004-290748 and JP-A-2004-290747.

The present inventors have found that synthetic quartz or fused quartz,which is silicon dioxide, has a photovoltaic ability, and have proposedthe silicon dioxide solar cell described in International PatentApplication Publication No. WO2011/049156.

The solar cell described in International Patent Application PublicationNo. WO2011/049156 is described with reference to FIG. 2.

In FIG. 2, numerals 11 and 17 represent 30 mm×30 mm glass substrateshaving a transparent conductive layer FTO (fluorine-doped tin oxide)layer 12 and an FTO layer 16, respectively, formed thereon, and thesolar cell has a size of 20 mm×20 mm.

An n-type semiconductor layer 13 of zinc oxide (ZnO), titanium dioxide(TiO₂), or the like is formed on the FTO layer on the light incidentside, and a platinum layer 15 is formed on the FTO layer 16 positionedopposite to the FTO layer 12 on the light incident side.

A solar cell material 20 having the thickness of 0.15 to 0.20 mm andhaving a mixture of glass containing SiO₂ and an electrolyte is sealedbetween the n-type semiconductor layer 25 and the platinum layer 26.

With respect to the solar cell material 27, there is used one which isobtained by immersing glass particles containing SiO₂ or the like in a5% aqueous solution of hydrofluoric acid for 5 minutes, washing theparticles with water, drying them, and pulverizing the resultantparticles so that the particle diameter becomes 0.2 mm or less.

The electrolyte is obtained by adding 0.1 mol of LiI, 0.05 mol of I₂,0.5 mol of 4-tert-butylpyridine, and 0.5 mol of tetrabutylammoniumiodide to 0.5 mol acetonitrile solvent.

While the details of the mechanism of silicon dioxide photocell areunclear, there is a phenomenon that when silicon dioxide is irradiatedwith the sunlight having the wavelength of 200 to 800 nm, the light isabsorbed and electrons flow from the electrode on the silicon dioxideside toward the counter electrode through a load, in other words, acurrent flows from the counter electrode toward the electrode on thesilicon dioxide side.

As a solar cell material, synthetic quartz is the most useful, but fusedquartz glass, soda-lime glass, non-alkali glass, or borosilicate glasscan also be used in electric generation.

The short-circuit current and open circuit voltage obtained whenirradiated with a light from a fluorescent lamp at 15,000 to 19,000 luxare as follows:

short-circuit current open circuit voltage Synthetic quartz: 0.5 μ A 35mV Fused quartz glass: 0.5 μ A 30 mV Socla-lime glass: 0.3 μ A 15 mVNon-alkali glass: 0.4 μ A 30 mV Borosilicate glass: 0.3 μ A 14 mV

Further, even with respect to the silicon dioxide composition which isnot treated with hydrofluoric acid, the following short-circuit currentand open circuit voltage have been obtained.

short-circuit current open circuit voltage Synthetic quartz: 0.1 μ A  3mV Fused quartz glass: 0.2 μ A  3 mV Soda-lime glass: 0.1 μ A  5 mVNon-alkali glass: 0.1 μ A  5 mV Borosilicate glass: 0.2 μ A 12 mV

PRIOR ART REFERENCES

Document 1: JP-A-2004-290748

Document 2: JP-A-2004-290747

Document 3: International Patent Application Publication No.WO2005/089941

Document 4: International Patent Application Publication No.WO2011/049156

DISCLOSURE OF THE INVENTION Object of the Invention

An object of the invention according to the present application is toobtain a solar cell which exhibits high light utilization efficiency.

The present inventors have found that by pulverizing thehalogen-acid-treated synthetic quartz particles or fused quartzparticles, further excellent solar cell function is exhibited.

The inventors have found that the synthetic quartz or glass pulverizedinto the powder size close to the light wavelength exhibits furtherexcellent function as a solar cell material.

The inventors have found that the silicon dioxide solar cell can alsoutilize the infrared light in electric generation.

In the invention of the present application, based on the abovefindings, there is obtained a solar cell having a combination of asilicon dioxide solar cell and a titanium dioxide solar cell in a tandemconfiguration, wherein power is extracted from both the electrodes onthe silicon dioxide solar cell side and on the titanium dioxide solarcell side, making it possible to utilize the light in all the regionfrom the ultraviolet light through the infrared light in the electricgeneration.

When the titanium dioxide solar cell in the tandem configuration is of adye sensitized type, the range of the usable light is widened.

The pulverized silicon dioxide powder particles may diffuse through theelectrolyte and adhere to the sensitizing dye, causing the function ofthe sensitizing dye to be poor.

In this case, a separator is provided between the silicon dioxide solarcell portion and the dye-sensitized titanium dioxide solar cell portion.

One aspect of the present application is a solar cell having acombination of a silicon dioxide solar cell and a dye-sensitizedtitanium dioxide solar cell in a tandem configuration, wherein thesilicon dioxide solar cell comprises synthetic quartz particles treatedwith halogen acid which are crystalline, or quartz glass, non-alkaliglass, borosilicate glass, soda-lime glass, or the like treated withhalogen acid which are amorphous, and an iodine electrolyte.

One aspect of the present application is a solar cell having acombination of a dye sensitized solar cell and a silicon dioxide solarcell in a tandem configuration, wherein the dye sensitized solar cellcomprises titanium dioxide having adsorbed thereon a dye, such as aruthenium dye, and an iodine electrolyte, and the silicon dioxide solarcell uses synthetic quartz particles treated with halogen acid which arecrystalline, or quartz glass, non-alkali glass, borosilicate glass,soda-lime, or the like treated with halogen acid which are amorphous.

One aspect of the present application is a solar cell having acombination of a dye sensitized solar cell and a silicon dioxide solarcell in a tandem configuration, wherein the dye sensitized solar cellcomprises porous titanium dioxide having adsorbed thereon a dye, such asa ruthenium dye, and an iodine electrolyte, and the silicon dioxidesolar cell uses synthetic quartz particles treated with halogen acidwhich are crystalline, or quartz glass, non-alkali glass, borosilicateglass, soda-lime glass, or the like treated with halogen acid which areamorphous, and the porous titanium dioxide is further combined withpulverized silicon dioxide.

Specific characteristic features of the silicon dioxide solar cell ofthe invention of the present application are as follows.

Two substrates having electrical conductivity are arranged so that therespective conductive surfaces of the substrates are facing each other,wherein at least one of the substrates is a transparent substrate on thelight incident side, and a silicon dioxide particles compact is disposedon the substrate arranged facing the substrate on the light incidentside, and the space between the silicon dioxide particles compact andthe substrate on the light incident side is filled with an electrolyte.

Two substrates having electrical conductivity are arranged so that therespective conductive surfaces of the substrates are facing each other,wherein at least one of the substrates is a transparent substrate on thelight incident side, and a silicon dioxide particles compact is disposedon the substrate facing the substrate on the light incident side, thespace between the silicon dioxide particles compact and the substrate onthe light incident side is filled with an electrolyte, and further aporous titanium dioxide sintered material is disposed on the substrateon the light incident side.

Two substrates having electrical conductivity are arranged so that therespective conductive surfaces of the substrates are facing each other,wherein at least one of the substrates is a transparent substrate on thelight incident side, and a silicon dioxide particles compact is disposedon the substrate facing the substrate on the light incident side, thespace between the silicon dioxide particles compact and the substrate onthe light incident side is filled with an electrolyte, and further aporous titanium dioxide sintered material having a sensitizing dyeadsorbed thereon is disposed on the substrate on the light incidentside.

Effects of the Invention

In the invention of the present application, by employing a combinationof a silicon dioxide solar cell and a titanium dioxide solar cell in atandem configuration, power is extracted from both the electrodes on thetitanium dioxide solar cell side and the silicon dioxide solar cellside.

By virtue of the above-mentioned configuration, the light in all theregion from the ultraviolet light through the infrared light can beutilized in the electric generation.

When the titanium dioxide solar cell in the tandem configuration is of adye sensitized type, the range of the usable light is widened.

The solar cell according to the present application can achieveincreased photo-generation than that obtained by a conventional solarcell comprising porous titanium dioxide and an iodine electrolyte.

The dye sensitized solar cell according to the present application canachieve increased photo-generation than that obtained by a conventionaldye sensitized solar cell comprising titanium dioxide having a rutheniumsensitizing dye adsorbed thereon and an iodine electrolyte.

The dye-sensitized titanium dioxide solar cell according to the presentapplication can achieve a short-circuit current of 2, 860 μA at most,and the electromotive ability has been drastically increased, ascompared to 2, 510 μA of a conventional dye-sensitized titanium dioxidesolar cell.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows diagrammatic views of a conventional porous titaniumdioxide solar cell and dye-sensitized porous titanium dioxide solarcell.

FIG. 2 shows a diagrammatic view of the prior art silicon dioxide solarcell.

FIG. 3 shows a diagrammatic view of the silicon dioxide solar cellaccording to Embodiment 1.

FIG. 4 shows a diagrammatic view of the solar cell according toEmbodiment 2 using porous titanium dioxide and silicon dioxide.

FIG. 5 shows a diagrammatic view of the solar cell according toEmbodiment 3 using dye-sensitized porous titanium dioxide and silicondioxide.

FIG. 6 shows a voltage-current characteristics graph of thedye-sensitized porous titanium dioxide solar cell according toEmbodiment 3 and a conventional dye-sensitized porous titanium dioxidesolar cell.

FIG. 7 shows a diagrammatic view of the arrangement of the silicondioxide solar cell according to Embodiment 4 using pulverized silicondioxide particles.

FIG. 8 shows a diagrammatic view of the arrangement of the solar cellaccording to Embodiment 5 using porous titanium dioxide and pulverizedsilicon dioxide particles.

FIG. 9 shows a diagrammatic view of the arrangement of the solar cellaccording to Embodiment 6 using dye-sensitized porous titanium dioxideand pulverized silicon dioxide particles.

FIG. 10 shows a diagrammatic view of the arrangement of the solar cellaccording to Embodiment 7 using porous titanium dioxide and pulverizedsilicon dioxide particles.

FIG. 11 shows a diagrammatic view of the arrangement of the solar cellaccording to Embodiment 8 using dye-sensitized porous titanium dioxideand pulverized silicon dioxide particles.

DESCRIPTION OF EMBODIMENTS

Hereinbelow, modes for carrying out the invention will be described withreference to the accompanying drawings.

Embodiment 1

FIG. 3 shows the silicon dioxide solar cell according to Embodiment 1,which is obtained by improving the silicon dioxide solar cell shown inFIG. 2.

In FIG. 3, numerals 11 and 17 represent glass substrates having atransparent conductive layer 12 made of FTO or the like and atransparent conductive layer 16 made of FTO or the like, formed thereonrespectively. The transparent conductive layer 12 and transparentconductive layer 16 function as an electrode for extracting electricpower. The glass substrates 11 and 12 are arranged so that thetransparent conductive layer 12 on the glass substrate 11 and the FTOlayer 16 on the glass substrate 17 are facing each other.

Numeral 20 represents a silicon dioxide (SiO₂) calcinated materialhaving the thickness of 0.15 to 0.20 mm, which is disposed on the glasssubstrate 17 on the side where light does not enter.

On the transparent conductive layer 16 on the silicon dioxide side, aplatinum (Pt) layer 15 is formed as an electrode for extracting charges.

Numeral 14 represents an electrolyte. In contrast to the prior artsilicon dioxide solar cell shown in FIG. 2 in which the electrolyte ismixed into silicon dioxide, the space between the silicon dioxidecalcinated material 20 and the glass substrate 11 on the light incidentside is filled with the electrolyte.

Numeral 18 represents a sealing material, and numeral 19 represents anexternal load.

In the electrolyte 14, there used an electrolyte obtained by adding 0.1mol of LiI, 0.05 mol of I₂, 0.5 mol of 4-tert-butylpyridine, and 0.5 molof tetrabutylammonium iodide to 0.5 mol acetonitrile solvent.

With respect to the silicon dioxide calcinated material 20, there isused a material obtained by immersing synthetic quartz which iscrystalline silicon dioxide, or glass particles of quartz glass,non-alkali glass, borosilicate glass, soda-lime, or the like, which areamorphous, in a 5% aqueous solution of hydrofluoric acid for 5 minutes,washing the particles with water, drying them, and then pulverizing theresultant particles so that the particle diameter becomes 500 nm orless.

With respect to the aqueous solution in which the silicon dioxide isimmersed, hydrochloric acid can be used as halogen acid other thanhydrofluoric acid.

The synthetic quartz particles having the particle diameter of about 0.2to 0.5 mm can be used, and those which are not calcined but are mixedwith ethanol and applied onto the platinum electrode 15 and dried canalso be used.

The light entered from the light incident side glass substrate 11 entersthe silicon dioxide 20 to cause electric generation.

Using a solar simulator, the solar cell according to Embodiment 1 wasirradiated with the light at 1 kw/m² which is a solar constant. When theparticle diameter of the synthetic quartz was 0.2 mm or less, ashort-circuit current of 85 μA and an open circuit voltage of 470 mVwere obtained. When the particle diameter was 500 nm or less, ashort-circuit current of 348 μA and an open circuit voltage of 620 mVwere obtained.

These values have been drastically increased with respect to both theshort-circuit current and open circuit voltage, as compared to thevalues of the prior art silicon dioxide solar cell shown in FIG. 2,although the measurement conditions are different from those for theembodiment.

In addition, with respect to the synthetic quartz solar cell which is asilicon dioxide solar cell, the present inventors measured ashort-circuit current at the illuminance almost equivalent to that ofdirect sunlight using a 300 W incandescent lamp which is a light sourcecontaining no ultraviolet region component. As a result, an open circuitvoltage of 400 mV and a short-circuit current of 0.5 μA were obtained,which has confirmed that the silicon dioxide solar cell causes electricgeneration using solely the infrared light.

From the above, it is apparent that the silicon dioxide solar cellcauses electric generation also using the light containing noultraviolet region component, where it is impossible for adye-sensitized titanium dioxide solar cell which is a typical wet-typesolar cell.

Embodiment 2

Embodiment 2 is described with reference to FIG. 4.

The solar cell according to Embodiment 2 is a combination of the silicondioxide solar cell according to Embodiment 1 and the conventionaltitanium dioxide solar cell shown in FIG. 1(a) in a tandemconfiguration.

In FIG. 4, numeral 11 represents a transparent substrate made of glassor a resin, forming on one surface thereof a transparent electrode layer12 made of FTO or the like, which serves as an electrode on a lightincident side. Numeral 3 represents a porous titanium dioxide solidifiedby a method, such as sintering. Numeral 14 represents an electrolyticsolution, where an iodine electrolyte having iodine dissolved in anaqueous potassium iodide solution is generally used.

Numeral 20 represents synthetic quartz particles having the particlediameter of 0.2 mm or less, which are mixed with ethanol and appliedonto an electrode 25 made of platinum or the like and dried.

Numeral 16 represents a transparent electrode made of FTO or the like,and numeral 17 represents a substrate made of glass or a resin. Numeral18 represents a sealing material, and numeral 19 represents an externalload.

The ultraviolet light entered from the transparent substrate 11 on thelight incident side enters the porous titanium dioxide 3 to causeelectric generation, and the ultraviolet light and visible light whichdo not contribute to the electric generation enter the silicon dioxide20 to cause electric generation.

Thus, the solar cell according to Embodiment 2 can utilize light in theregion from the ultraviolet light through the visible light in electricgeneration.

When the solar cell according to Embodiment 1 is irradiated with lightat 1 kw/m2, which is a solar constant, using a solar simulator, ashort-circuit current of 20 μA and an open circuit voltage of 417 mV areobtained.

Embodiment 3

Embodiment 3 is described with reference to FIG. 5.

The solar cell according to Embodiment 3 is a combination of the silicondioxide solar cell according to Embodiment 1 and the conventionaldye-sensitized titanium dioxide solar cell shown in FIG. 1(b) in atandem configuration.

In FIG. 5, numeral 11 represents a transparent substrate made of glassor a resin, forming on one surface thereof a transparent conductivelayer 12 made of FTO or the like, which serves as an electrode on alight incident side.

Numeral 10 represents a porous titanium dioxide which is solidified by amethod, such as sintering, and which has adsorbed thereon a sensitizingdye, such as a ruthenium complex dye.

Numeral 14 represents an electrolytic solution, and an iodineelectrolyte having iodine dissolved in an aqueous potassium iodidesolution is generally used.

Numeral 20 represents pulverized synthetic quartz particles having theparticle diameter of 500 nm or less, which are mixed with ethanol andapplied onto an electrode 15 made of platinum or the like and dried.

Numeral 16 represents a transparent electrode made of FTO or the like,and numeral 17 represents a substrate made of glass or a resin. Numeral18 represents a sealing material, and numeral 19 represents an externalload.

Among the ultraviolet light through infrared light entered from thetransparent substrate 11 on the light incident side, the ultravioletlight through visible light enters the dye-sensitized porous titaniumdioxide 10 to cause electric generation, and the ultraviolet lightthrough infrared light which does not contribute to the electricgeneration enters the silicon dioxide 20 to cause electric generation.

As mentioned above in connection with Embodiment 1, the silicon dioxide20 causes electric generation using even light in the region from thevisible light through the infrared light, where the titanium dioxide andsensitizing dye do not cause the electric generation.

Thus, the solar cell according to Embodiment 3 can utilize the light inall the region from the ultraviolet light through the infrared light inelectric generation.

By the solar cell according to Embodiment 3, a short-circuit current of285 μA and an open circuit voltage of 510 mV are obtained.

FIG. 6 shows the voltage-current characteristics of the dye sensitizedsolar cell when varying the silicon dioxide and the voltage-currentcharacteristics of the conventional dye sensitized solar cell.

In FIG. 6, the voltage is taken as the abscissa, and the current istaken as the ordinate.

In the graph, for example, indication “1.0E-03” means 1.0 mA.

The characteristics are results of the measurement of a voltage and acurrent between the FTO electrodes using a solar simulator at theincident light energy of 1-Sun (i.e., 1 kW/m²) on the solar cell.

FIG. 6 shows voltage-current characteristics curves of 6 samples A to Eand G and a conventional dye sensitized solar cell F which is acomparative sample.

Character A indicates a voltage-current characteristics curve obtainedwhen using the synthetic quartz particles pulverized so as to have theparticle diameter of 50 to 200 nm, in which the short-circuit current is3,067 μA and the open circuit voltage is 660 mV.

Character B indicates a voltage-current characteristics curve obtainedwhen using the synthetic quartz particles having the particle diameterof 0.2 mm, in which the short-circuit current is 2,340 μA and the opencircuit voltage is 680 mV.

Character D indicates a voltage-current characteristics curve obtainedwhen using fused quartz, in which the short-circuit current is 1, 293 μAand the open circuit voltage is 680 mV.

Character C indicates a voltage-current characteristics curve obtainedwhen using non-alkali glass, in which the short-circuit current is 1,850μA and the open circuit voltage is 690 mV.

Character E indicates a voltage-current characteristics curve obtainedwhen using borosilicate glass, in which the short-circuit current is 930μA and the open circuit voltage is 700 mV.

Character F indicates a voltage-current characteristics curve of theconventional dye sensitized solar cell of FIG. 1(b), in which theshort-circuit current is 733 μA and the open circuit voltage is 680 mV.

Character G indicates a voltage-current characteristics curve obtainedwhen using soda-lime glass, in which the short-circuit current is 626 μAand the open circuit voltage is 670 mV.

As can be seen from these voltage-current characteristics curves, thedye sensitized solar cells using the silicon dioxide in A to E canextract the larger current, comparing to the conventional solar cell.

Further, even in the case using soda-lime glass which generally seems tobe poorer than the conventional solar cell, in some voltage region, thesolar cell can extract the larger current than that achieved by theconventional solar cell.

Embodiment 4

In Embodiment 1 shown in FIG. 3, the pulverized synthetic quartzparticles to be used have the particle diameter as small as 500 nm orless, and, when the synthetic quartz particles applied onto the platinumelectrode are dried and brought into contact with an electrolyticsolution, the particles may be dispersed or suspended in theelectrolytic solution as indicated by numeral 22 in FIG. 7.

The current-voltage relationship of the silicon dioxide solar cell isnot strongly affected even in such the state.

Embodiment 5

In Embodiment 2 shown in FIG. 4, the pulverized synthetic quartzparticles to be used have the particle diameter as small as 500 nm orless, and, when the synthetic quartz particles applied onto the platinumelectrode are dried and brought into contact with an electrolyticsolution, the particles may be dispersed or suspended in theelectrolytic solution as indicated by numeral 22 in FIG. 8.

The current-voltage relationship of the silicon dioxide solar cellhaving a porous titanium dioxide sintered material combined is notstrongly affected even in such the state.

Embodiment 6

In Embodiment 3 shown in FIG. 5, the pulverized synthetic quartzparticles to be used have the particle diameter as small as 500 nm orless, and, when the synthetic quartz particles applied onto the platinumelectrode are dried and brought into contact with an electrolyticsolution, the particles may be dispersed or suspended in theelectrolytic solution as indicated by numeral 22 in FIG. 9.

The current-voltage relationship of the silicon dioxide solar cellhaving a dye-sensitized porous titanium dioxide sintered materialcombined is not strongly affected even in such the state.

Embodiment 7

FIG. 10 shows the silicon dioxide solar cell according to Embodiment 6which is obtained by improving Embodiment 5.

In Embodiment 6, the pulverized synthetic quartz particles dispersed orsuspended in the electrolytic solution have the particle diameter assmall as 500 nm or less and are a poor conductor in essence, andtherefore, may possibly penetrate into the pore portions of the poroustitanium dioxide to inhibit the ability of the titanium dioxide togenerate electricity.

For preventing the occurrence of such the above accident, using aseparating membrane 23 permeable only for the electrolyte, theelectrolyte in which the silicon dioxide 22 is suspended and theelectrolyte in which the silicon dioxide 22 is not suspended areseparated from each other.

Embodiment 8

FIG. 11 shows the silicon dioxide solar cell according to Embodiment 6which is obtained by improving Embodiment 6.

In Embodiment 6, the pulverized synthetic quartz particles dispersed orsuspended in the electrolytic solution have the particle diameter assmall as 500 nm or less and are a poor conductor in essence, andtherefore, may possibly penetrate into the pore portions of the poroustitanium dioxide to inhibit the ability of the titanium dioxide togenerate electricity.

For preventing the occurrence of such the above accident, using aseparating membrane 23 permeable only for the electrolyte, theelectrolyte in which the silicon dioxide 22 is suspended and theelectrolyte in which the silicon dioxide 22 is not suspended areseparated from each other.

Embodiment 9

In the invention of the present application, with respect to thesubstrate, transparent conductive layer, counter electrode, electrolyte,and the like, various arrangements and materials other than thosedescribed in the aforementioned Embodiments can be used.

Hereinbelow, the arrangements and materials usable as substitutes aredescribed.

[Substrate]

In each of the Embodiments, with respect to the container containingtherein the solar cell material and electrolyte, a light transmissivematerial is used on the light incident side, and a light transmissive ornon-transmissive material is used on the side to which no incident lightenters.

As a light transmissive material, glass, plastics, amorphous silicon, ora polyester film can be used, and, as a light non-transmissive material,a metal plate of stainless steel, nickel, or the like is used.

[Transparent Conductor]

Almost all the glass and plastics used as a light transmissive materialhave no electrical conductivity, and, when using a material having noelectrical conductivity, it is necessary to impart electricalconductivity to the material. As a light transmissive material havingelectrical conductivity, in addition to tin oxide, such as FTO or ITO,AZO (Al—ZN—O), a carbon material, such as carbon nanotubes or graphene,or a conductive PET film is used, and an electrode formed on atransparent material of glass, plastics, or the like is used. Thetransparent electrode is provided inside the solar cell.

With respect to the side of the solar cell container opposite to thelight incident side, when it is required to transmit the light, atransparent electrode made of FTO, ITO, carbon nanotubes, graphene, orthe like formed on a transparent material of glass, a plastic, or thelike is used, and, when it is not required to transmit the light, ametal plate forming thereon a conductor for extracting charges made ofcarbon nanotubes, graphene, or the like is used. The conductor forextracting charges is provided inside the solar cell.

When conductive plastics is used as the plastics, the transparentconductor can be omitted.

[Silicon Dioxide Particles]

The halogen acid-treated crystalline synthetic quartz particles oramorphous glass particles are prepared as follows.

Synthetic quartz which is crystalline silicon dioxide (SiO₂), or glassparticles of quartz glass, non-alkali glass, borosilicate glass,soda-lime, or the like, which is amorphous silicon dioxide, are immersedin an aqueous solution of hydrofluoric acid, and the resultant syntheticquartz particles or glass particles are washed with water and thendried, followed by pulverization.

Hydrochloric acid is used as halogen acid other than hydrofluoric acid,but hydrofluoric acid is preferred.

Alternatively, other halogen acid can be used.

When the silicon dioxide particles are not treated with halogen acid, asample of the silicon dioxide particles is pulverized so that theaverage particle diameter of the particles becomes several 10 nm.

The treatment of the silicon dioxide particles with halogen acid can beperformed after the pulverization but not before the pulverization.

[Silicon Dioxide Layer]

With respect to the silicon dioxide layer, there can be used a layerobtained by mixing synthetic quartz powder with ethanol together withplatinum powder and subjecting the resultant mixture to calcination.

The silicon dioxide particle calcinated material having the particlediameter of up to about 0.5 mm can be used.

[Electrolyte]

With respect to the electrolyte, as a supporting electrolyte, varioustypes of electrolytes, e.g., cations, such as lithium ions, or anions,such as chloride ions, are used, and, as oxidation-reduction pairpresent in the electrolyte, an oxidation-reduction pair, such as aniodine-iodine compound or a bromine-bromine compound, is used.

0.4 mol of 1-ethyl-3-methylimidazolium iodide, 0.4 mol oftetrabutylammonium iodide, 0.2 mol of 4-tert-butylpyridine, and 0.1 molof guanidine isothiocyanate are dissolved in propylene carbonate liquidas a solvent to prepare an electrolyte.

When the concentration of halogen molecules in the electrolyte is 0.0004mol/L or less, the electrolyte is almost colorless and transparent inthe visible light region.

0.5 mol of lithium iodide (LiI) and 0.05 mol of metallic iodine (I₂) aredissolved in methoxypropionitrile, and thickener is added to theresultant solution, and further 4-tert-butylpyridine is added theretofor improving the open electromotive ability and fill factor.

When the composite glass plate needs neither be colorless nortransparent, colored electrolytic solution, such as the iodineelectrolytic solution, can be used.

Organic acid, such as acetic acid or citric acid, can be used as thecolorless electrolyte.

[Sensitizing Dye]

By using sensitizing dye, the titanium dioxide solar cell can utilizelight in the ultraviolet light and visible light region in electricgeneration. When the silicon dioxide solar cell satisfactorily causeselectric generation using the light in the visible light region, it isnot necessary to use expensive sensitizing dye having a short life.

With respect to the sensitizing dye other than the ruthenium complexdye, cobalt complex dye, porphyrin, cyanine, merocyanine,phthalocyanine, coumarin, riboflavin, xanthene, triphenylmethane, azo,quinone, C60 derivative, BTS (styryl benzothiazolium propylsulfonate),indoline, or dye derived from a plant, such as hibiscus or Americancherry, can be used, and, by choosing from the dye having differentelectric generation properties, the light usable in the electricgeneration can be appropriately selected.

[Counter Electrode]

With respect to the semiconductor layer as a counter electrode, otherthan the zinc oxide (ZnO), titanium dioxide (TiO₂), copper oxide (CuO),magnesium oxide (MgO), strontium titanate (SrTiO₃), carbon nitride,graphene, or the like can be used.

[Surface on the Light Incident Side]

In all the Embodiments described above, the silicon dioxide calcinatedmaterial is disposed on the side to which no incident light enters.There is no absolute reason for this arrangement, and therefore thesilicon dioxide calcinated material can be disposed on the side to whichthe incident light enters.

INDUSTRIAL APPLICABILITY

According to the invention of the present application, combining furthera silicon dioxide solar cell in a tandem configuration in a titaniumdioxide solar cell container, there can be obtained a solar cell whichis advantageous in that it can utilize light in all the region from theultraviolet light through the infrared light in electric generation.

REFERENCE NUMERALS

-   1, 7, 11, 17: Substrate-   2, 6, 12, 16: Transparent conductive layer-   3: Porous titanium dioxide sintered material-   4, 14: Electrolyte-   5, 15: Counter electrode-   8, 18: Sealing material-   9: External load-   10: Dye-sensitized porous titanium dioxide sintered material-   20: silicon dioxide particles compact-   22: Silicon dioxide particles

The invention claimed is:
 1. A silicon dioxide solar cell, comprising:first and second substrates having electrical conductivity, the firstsubstrate having a negative electrode, the second substrate having apositive electrode, respectively, the first and second substrates beingarranged so that the negative and positive electrodes of the first andsecond substrates are facing each other, the first substrate being atransparent substrate on a light incident side to which a light isirradiated; a layer made of silicon dioxide particles; and anelectrolyte disposed between said first and second electrodes, whereinsaid layer made of silicon dioxide particles is disposed at the positiveelectrode on a side of the second substrate, a space between said layermade of silicon dioxide particles and said first substrate on the lightincident side is filled with said electrolyte, and the silicon dioxidesolar cell is configured to generate electricity from the silicondioxide particles in said layer made of silicon dioxide particles. 2.The silicon dioxide solar cell according to claim 1, wherein the silicondioxide particles have the particle diameter of 500 nm or less.
 3. Thesilicon dioxide solar cell according to claim 1, wherein the silicondioxide particles are treated with halogen acid.
 4. The silicon dioxidesolar cell according to claim 3, wherein the halogen acid ishydrofluoric acid.
 5. The silicon dioxide solar cell according to claim3, wherein the halogen acid is hydrochloric acid.
 6. The silicon dioxidesolar cell according to claim 1, wherein said layer made of silicondioxide particles comprises silicon dioxide particles selected from thegroup consisting of synthetic quartz particles, fused quartz glassparticles, borosilicate glass particles, and soda-lime glass particles.7. The silicon dioxide solar cell according to claim 1, wherein a poroustitanium dioxide sintered material is disposed on said negativeelectrode of the first substrate on the light incident side.
 8. Thesilicon dioxide solar cell according to claim 7, wherein the poroustitanium dioxide sintered material has adsorbed thereon sensitizing dye.9. The silicon dioxide solar cell according to claim 1, wherein thesilicon dioxide solar cell is capable of electricity generation fromsaid layer made of silicon dioxide particles in response to a lightwhich does not contain ultraviolet.
 10. The silicon dioxide solar cellaccording to claim 1, wherein the positive electrode is a platinumelectrode.